T-square



April 15, 1941. DE LIISLE 7 2,238,581

II-SQUARE Filed June 26, 1939 I as x Patented Apr. 15, 1941 UNITED STATES PATENT OFFICE T-SQUARE Harold L. De Lisle, Sheboygan, Wis.

Application June 26, 1939, Serial No. 281,116

8 Claims.

This invention relates to T-squares more particularly for use by mechanical draftsmen or the like, and aims to provide an improved device of this class.

Among other objects, the invention contemplates the provision of a movable head, and in one aspect, a pair of such heads. By this arrangement space is saved in shipping or stocking the T-squares and, furthermore, one of the heads may be arranged to swivel so as to afford relative angular adjustments of the head and blade.

In accordance with the present invention the blade of the improved T-square may be separable from at least one of the heads, for example, the swivel head, so that the device may be used with or without the latter. Furthermore, common means are advantageously contemplates for securing or pivoting the heads to the blade, thus effecting economy and simplicity.

The invention also desirably includes means for rectifying the straight edge of the head if variations occur from constant use.

Other objects and advantages will be apparent from the following description taken together with the accompanying drawing, in which Figure 1 is a partial plan view of the blade and one of the heads, an alternative selective position of this head being shown in broken lines;

Figure 2 is an enlarged partial longitudinal section taken on the line 2-2 of Fig. 1;

Figure 3 is an exploded fragmentary view of parts shown in Figs. 1 and 2, slightly less enlarged than Fig. 2;

Figure 4 is a perspective view of another head for the device with associated parts in separated relation, on the scale of Fig. 1;

Figure 5 is a still further enlarged cross-section taken on the line 55 of Fig. l but also showing the parts of Fig. 4 associated with the structure of Fig. 1; and

Figure 6 is an enlarged plan view of the lower part shown in perspective in Fig. 4.

In the illustrative construction shown in the drawing, I'll is in general the elongated blade (discontinued at its right-hand end to save space) of a draftsmans T-square, and II isa head therefor. This head I I may occupy with respect to the blade [0 one of two alternative positions either at ninety degrees with respect to the blade as shown in full lines in Fig. 1 or at one hundred and eighty degrees, that is, parallel thereto, as shown in broken lines. The head and central longitudinal part In of the blade are desirably formed of a phenolic condensation product such as Bakelite, andthe straightedges l2 of the blade may be advantageously made of Celluloid or such transparent material dove-tailed into the main body of the blade as at [3 and of slightly less thickness than the blade, as is well known in the art.

In accordance with the present invention the blade at its left-hand end is perforated as at M and the head II is similarly perforated as at I5 to provide a bearing for an interiorly threaded sleeve l6 which is one of the parts for securing the head and blade together. Surrounding the perforation I4 in the blade is a metal plate I! which is desirably square and which at its four corners is secured by pins 18 to the upper face of the blade, the pins I8 extending through the blade to project slightly from its under face as at l9. These pins are arranged to define a square, the center of which is a perforation 20 in the plate I! registering with the perforation M in the blade and two sidesof which are parallel to the straight edges I2 01 theblade. The pins l8 desirably have a tight drive fit in the.blade.,

The head II has not only the perforation l5 registering with the perforations I4 and 20 but also has pin holes 2| adapted to register with the lower ends IQ of the pins l 8.

Since the pin holes 2| are arranged in a square passes through the under. side of the head and' into the threaded sleeve l6. Since this sleeve l6 has a flangedpart 24 which laps the plate I! on the upper face of the blade, the parts are thus clamped together as best shown in Fig, 2, a washer 25 being desirably inserted betweenthe screw 23 and the lower face of the head tomini mize wear thereon.

The device thusv far described is a complete T-square and may be used as such, when the parts are in full line position shown inFig. 1, after having been shipped or stored in dotted line position.

Since it has been found that constant use 5f the T-square tends to wear the ends of the head at the points 26 on the straight. edge surface 22,

the present invention contemplates means for.

correcting a deviation from the straightat these points. For this purpose the head II is shown split from its rear edge 21 inwardly to the perforation l5 as at 28 and within this split means are provided for spreading the head in the vicinity of the split, such means being here represented by the set-screw 29. which is screwed into a pair of opposed semi-cylindrical cuts forming jointly a bore 30 in the head concentric with the split 28.

By tightening this set-screw 29, that is, by screwing it further into the head, the surfaces 26 are forced in a direction away from the rear surface 21 of the head and into line with the straight edge 22 to compensate for wear thereon.

When, now, it is desired to include a swivel head in the combination, the head 3| may be used which may be substantially the same in size and shape as the head II, and have the perforation 32 centrally therein to register with the perforations M, I and 20 already described.

In accordance with the present invention, the sleeve l6 provides common means for securing both the head II and the head 3| to the blade, and for this purpose a knurled thumb stud 33 has a threaded shank 34 which is received in the interiorly threaded sleeve l6 similarly to the screw 23 but from the opposite or upper end, the shank 34 passing rotatably through the perforation 32.

In order to reduce the space occupied by the parts,'the under face of ,thehead 3| has a cylindrical recess 35 which rotatably receives the flanged part 24 of the sleeve l6. Also margining the recess 35 is desirably another cylindrical recess or counterbore 36 in the face of the head 3| which houses a friction-producing member as here shown in the form of a pronged ring 31, the prongs 38 of which are tilted as best shown at 39, so as both to grip the wall of the recess 38, into which they may be pressed, and also to scrapihgly engage the plate I! aboutits perforation 20 when the knurled stud 33 is tightened to clamp the parts together, as best shown in Fig. 5. A washer 40 may be inserted between the stud and the upper face of the head 3| to minimize wear at this point.

Thus the head 3| 'rnay be adjusted by means of releasing and then clamping the thumb-stud 33 at any relativeselective angularposition infinitely with respect to the blade ||l while the head may be fixed at the right-angular position as shown in full lines in Fig. 1. vAs is Well known in the art, the T-square may be reversed either to use one of the heads such as the head I l as a right-angle T-square, or to use the head 3| for drawing parallel lines at an angle, for example.

7 having registering pivotal perforations, a plate margining the perforation in said blade, a threaded sleeve having a shank part passing through said perforations in the plat-e and blade, and having a flanged part lapping said plate, a circular recess in the head margining the perforation in the head and rotatably receiving the flanged part of said sleeve, and a knurled stud passing through the perforation in the head and threadedly received in said sleeve.

4. The structure of claim 3 wherein there is a pronged friction-producing member also margining said perforation in the head and adapted to frictionally engage said plate when the stud is screwed into the sleeve.

5. The structure of claim 3 wherein the said plate is secured to -the blade by pins which pass through the blade and project upon its opposite H or the straight edge 43 of the head 3|, de-

pending upon which head is being used, will engage the edge of the drawing board.

The under face of the blade may have a longitudinal groove 4| therein to minimize friction upon the table top when the T-square is used and also to minimize warping of the blade, and the straight edge 22 of the head may have a depression 42 therein aligned with the slit 28 to facilitate action of the head under the influence of the set-screw 29 as already described.

So constructed and arranged, with a minimum number of parts the T-square may be used with or without the swivel head. In fact, it is feasible to sell the T-square in large quantities without the swivel head, and its associated parts shown in Fig. 4, and later the purchaser of the T-square may obtain the swivel head parts to incorporate with the device with economy of both parts and cost.

Having described my invention, I claim 1. As an article. of manufacture, a T-square embodying a blade and a head movable with re spect to the blade. wherein the blade and head areperforated for the reception of a pivot memher and the head is of somewhat resilient material and is split from its rear edge to its said perforation and wherein the head carriesmeans for spreading the said split against the resilience of the head material.

surface and are adapted to be received in pin holes in a second head.

6. The structure of claim 3 wherein the said plate is secured to the blade by pins which pass through the blade and project upon its opposite surface and are adapted to be received in pin holes in a second head, and wherein the said second head is also clamped to said blade by a screw threadedly received in said sleeve.

'7. In a T-square, the combination of a blade having a pair of removable heads, common means for fixing the heads to the blade including a sleeve open at both ends and interiorly threaded substantially throughout its length, said sleeve having a flanged part at one end and a shank part, said flanged part. being adapted to lap the blade, perforations in the blade and one of the heads receiving said shank part therethrough, a clamping screw threadedly received in the sleeve shank part from its end opposite its flanged part for clampingthehead receiving the shank part therethrough to the blade, a perforation in the other head, and a second clamping screw passing therethrough and threadedly into the sleeve at its flanged end.

8. In a T-square, the combination of a blade having a removable head, means for fixing the head to the blade including a member threaded at both ends, said member having a flanged part at one end and a shank part, perforations in the blade and head receiving said shank part, the

flanged part lapping the blade upon its side opposite to the head, and a clamping screw having threaded engagement with the shank part at the shank part end opposite the flanged part for clamping the head to the blade, said member being interiorly threaded at its flanged end and open at its flanged end to threadedly receive another clamping screw in its flanged end to clamp a second head to the blade, whereby the second head may swivel on the blade.

HAROLD L. DE LISLE. 

